[env-trinity] CBB: Salmon Survival: It’s All About The Early Days In The Ocean And 2010 Tough To Call

[Sari Sommarstrom]

Columbia Basin Bulletin


Salmon Survival: It’s All About The Early Days In 
The Ocean And 2010 Tough To Call
Posted on Friday, January 07, 2011 (PST)

Ocean conditions off the coast of Oregon and 
Washington changed from nightmarish to dreamy for 
juvenile salmon this past late spring-early 
summer and in the process confounded experts’ 
efforts to predict how those young fish may have fared.



“The fact that ocean conditions were poor early 
in the season but great later in summer makes it 
impossible to provide any reliable forecast this 
year: our best ‘guess’ is that we can expect near 
‘average’ returns in 2011 (for coho) and 2012 
(for chinook),” according to the Northwest 
Fisheries Science Center’s annual qualitative 
prediction of future returns. “We do not think 
that the El Niño had a devastating effect on 
salmon because the warm ocean conditions at the 
time of ocean entry (in April/May) were about ‘average.’”



NOAA Fisheries’ NWFSC has over the past 13 years 
developed a suite of ocean ecosystem “indicators” 
that are monitored and the data then used to 
estimate what kind of an impact they might have 
had on juvenile salmon during the earliest stage 
of their ocean sojourn. Basically, the better the 
survival early on, the more fish are expected to 
survive to adulthood to return to the Columbia River basin to spawn.



Each of the 18 or so indicators is rated for the 
year as good, neutral or bad. Then they are 
compared individually to past measurements and, 
as was the case this year, given a score of from 
1 (the best combined score over the course of the study) to 13 (the worst).



The run-size forecasts are based on the average 
score for the indicators overall.



The mean of those scores for 2010 ranked the year 
eighth out of 13, which would indicate slightly 
below average overall conditions for coho and 
spring chinook salmon that ventured to sea last 
spring. The forecasts are for the first year that 
species’ begin to return as fully matured adults, 
in the coho’s case after one year in the Pacific 
and the spring chinook after two years.



“There’s some hints that it was not that 
terrible” for young fish that typically would 
have entered the ocean before conditions turned 
from bad to good, said Bill Peterson, NOAA 
Fisheries oceanographer and senior scientist. The 
number of coho jacks that returned, as counted at 
Bonneville Dam, after just a few months in the 
ocean was in the average range, he said. The 
strength of a jack return can mirror the strength 
of broodmate returns in succeeding years.



In the California current that hugs the coast, 
and elsewhere, cold is good for salmon.



“Because of the 2009-10 El Niño event, the ocean 
began to warm in autumn 2009 and remained warm 
through April 2010, after which a cooling trend 
resumed in May 2010,” the forecast says. The El 
Nino/Southern Oscillation is the measure of sea 
surface temperatures in the equatorial Pacific 
that can affect climate worldwide.



“Thus, 2010 began as a ‘warm year,’ began to cool 
in May but by July, the ocean was the coldest 
observed in recent years. Thus we had very mixed 
signals in 2010 making it difficult to offer any 
reliable outlooks in returns of coho salmon in 
2010 and chinook salmon in 2012,” the forecast says.



“During the tail end of the El Niño, in May and 
June, we had some of the worst ocean conditions 
we’ve seen in the 13 years we’ve been sampling,” 
Peterson said. “Then in July, the conditions were 
as good as they’ve ever been. So it’s a question 
of timing” and what the fish did once they entered the ocean.



Coho tend to hang out not too far off the coast 
and not too deep. The spring chinook don’t seem 
to dawdle too long before charging north up the 
continental shelf to parts unknown.



At the time of the young fishes entry, “the ocean 
really was kind two-layered” with warm surface 
water and cool water deeper that was relatively 
plentiful in terms of nutrients on which juvenile salmon feed.



Survival may have depended on “if they had enough 
sense to go deeper,” Peterson said. Coho and 
steelhead have a more shallow orientation than chinook.



“Vertical structure is really something we’ve 
really not thought about,” Peterson said.



For the past 13 years, Peterson and his 
colleagues have conducting trawl surveys funded 
by the Bonneville Power Administration in June 
and September from Cape Perpetua to La Push, 
Wash., counting the abundance of juvenile salmon 
along the near-shore waters of the West Coast. 
The survival rate of juvenile salmon is the key 
indicator for future salmon runs, says Peterson.



When salmon first enter the ocean, they must have 
enough food to not only survive, but to grow 
rapidly enough to avoid predation. The smaller 
they are, the more vulnerable they are to 
potential predators lurking offshore. And when 
ocean productivity is high, populations of other 
fish like herring, anchovies and sardines grow 
and provide alternatives for the predators.



Peterson said the juvenile chinook counted this 
summer was the fifth highest they’ve had in their 
13 years, raising hope for future chinook runs. 
But the season’s mixed bag continued



“We caught almost no juvenile coho salmon in 
September and that worries me,” Peterson said.



“We’ll find out soon enough,” he said. “Coho 
return as adults after 18 months; spring chinook 
come back after two years and fall chinook, three 
years or longer. If these fish can make it to 
adulthood, they should be fine. There’s not much 
that out there that feeds on them other than sea lions and orcas.



“It’s all about how they fare as youngsters,” he 
added, “and the jury is definitely still out this year.”



If the cool La Nina and negative Pacific Decadal 
Oscillation keep their grip, conditions should be 
much improved by the time this year’s class ventures out.



SST anomalies were consistently colder than 
normal by several degrees during the summer of 
2010 and the deep water temperatures on the 
continental shelf in July-August were the coldest of the 13-year record.



And the biomass of the lipid-rich “northern” 
copepod species was the third highest on record 
during the summer of 2010. The northern copepods 
are a key link in the food chain.



The negative signals dominated early in the 
spring-summer season. The PDO was positive 
(generally considered bad for salmon) and SSTs 
were warm during the winter of 2009-2010 
indicating poor ocean conditions during the winter.



The PDO is a climate index based upon patterns of 
variation in sea surface temperature of the North 
Pacific from 1900 to the present. While derived 
from sea surface temperature data, the PDO index 
is well correlated with many records of North 
Pacific and Pacific Northwest climate and 
ecology, including sea level pressure, winter 
land-surface temperature and precipitation, and 
stream flow,” according to information posted on 
NWFSC’s “Ocean Ecosystem Indicators of Salmon 
Marine Survival in the Northern California 
Current” web site. That site is located at:

http://www.nwfsc.noaa.gov/research/divisions/fed/oeip/a-ecinhome.cfm



The index is also correlated with salmon landings 
from Alaska, Washington, Oregon and California.



“Although the winter storms ended in late March 
and the upwelling season was initiated on 5 
April, strong upwelling was not initiated until 
two months later, on 9 June,” according to the 
forecast. The length and strength of the 
upwelling is indicative of the availability of 
fish food delivered to the surface.



“Within that two months period several southwest 
storms moved through the region. This is 
generally a negative sign for salmon that enter 
the ocean in April-May,” the forecast says.



“Copepod species richness was very high during 
winter-spring-summer of 2010, ranking 11 of 13 
from May-September. We regard this as a negative 
sign because it indicates that the sub-tropical 
species that were brought to Oregon with the El 
Niño persisted for several months after the end 
of the El Niño event; species richness did not 
return to normal until autumn 2010.”


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